Base station and broadcast channel transmission method

ABSTRACT

A disclosed base station transmits a broadcast channel to a user device a predefined number of times in a predetermined cycle for communication with the user device. The base station includes a repetition unit configured to repeat the broadcast channel, after the broadcast channel is channel-coded, for the predefined number of times to generate multiple broadcast channels; and a signal waveform changing unit configured to process the generated broadcast channels such that the processed broadcast channels have different signal waveforms. Positions of the broadcast channels in the order of transmission in the predetermined cycle are associated with the signal waveforms of the broadcast channels.

TECHNICAL FIELD

The present invention generally relates to a radio communication system.More particularly, the present invention relates to a base station and abroadcast channel transmission method.

BACKGROUND ART

A successor communication system to W-CDMA and HSDPA, i.e., Long TermEvolution (LTE), is currently being discussed by 3GPP, a standardizationgroup for W-CDMA. In LTE, orthogonal frequency division multiplexing(OFDM) is to be used as a downlink radio access method andsingle-carrier frequency division multiple access (SC-FDMA) is to beused as an uplink radio access method (see, for example, 3GPP TR 25.814(V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006).

In OFDM, a frequency band is divided into multiple narrow frequencybands (subcarriers) and data are transmitted on the subcarriers. Thesubcarriers are densely arranged along the frequency axis such that theypartly overlap each other but do not interfere with each other. Thismethod enables high-speed transmission and improves frequencyefficiency.

In SC-FDMA, a frequency band is divided into multiple frequency bandsand the frequency bands are allocated to different terminals fortransmission in order to reduce interference between the terminals.Also, SC-FDMA reduces variation of the transmission power and thereforemakes it possible to reduce power consumption of terminals and toachieve wide coverage.

In uplink and downlink of LTE, one or more physical channels are sharedby multiple user devices for communication. A channel shared by multiplemobile stations is generally called a shared channel. In LTE, a physicaluplink shared channel (PUSCH) is used for uplink and a physical downlinkshared channel (PDSCH) is used for downlink.

In a communication system employing shared channels, it is necessary tosignal allocation information of the shared channels to user devices foreach subframe (1 ms in LTE). In LTE, a control channel used to signalthe allocation information is called a physical downlink control channelor a downlink (DL) L1/L2 control channel. The physical downlink controlchannel, for example, includes downlink (DL) scheduling information,acknowledgement information (ACK/NACK), an uplink (UL) scheduling grant,an overload indicator, and a transmission power control command bit(see, for example, R1-070103, Downlink L1/L2 Control Signaling ChannelStructure Coding).

Meanwhile, broadcast channels include a first broadcast channel (primarybroadcast channel (P-BCH)) and a dynamic broadcast channel (D-BCH).

The primary broadcast channel is transmitted using a fixed transmissionmethod as in the case of a broadcast channel in W-CDMA. The primarybroadcast channel is used to report minimum basic information. Thedynamic broadcast channel is used to report information other than theinformation reported by the primary broadcast channel. The dynamicbroadcast channel is transmitted via a shared data channel.

There is a consensus to transmit the primary broadcast channel at acycle of “x” ms, and it has been proposed to set “x” at 40 (see, forexample, R2-072183, System Information, May 2007). Also, there is aconsensus to transmit the same control information “M” times within thecycle of “x” ms for transmitting the primary broadcast channel, and ithas been proposed to set “M” at 2 or 4. Each transmission of the controlinformation is called a burst.

For example, if the primary broadcast channel is to be transmitted fourtimes in a cycle of 40 ms, it means that the primary broadcast channelis transmitted every 10 ms as shown in FIG. 1.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, the above background art technologies have problems asdescribed below.

Although there is a consensus to transmit the primary broadcast channelat a cycle of “x” ms (hereafter called a primary broadcast channeltransmission cycle), it has not been determined how to transmit theprimary broadcast channel in the primary broadcast channel transmissioncycle. In the primary broadcast channel transmission cycle, the sameinformation is transmitted repeatedly as the primary broadcast channel.When it is necessary to transmit different information, the informationto be transmitted is changed at the boundary between primary broadcastchannel transmission cycles.

In the example shown in FIG. 1, the primary broadcast channeltransmitted every 10 ms in one primary broadcast channel transmissioncycle includes the same control information. In this case, the mobilestation can detect the boundary between 10 ms intervals in a cellsearch, but cannot detect the boundary between primary broadcast channeltransmission cycles of 40 ms.

Methods for mapping the primary broadcast channel include an “all bitsspread over all bursts” method where all bits are spread over all burstsand an “all bits in each burst” method where all bits are transmitted ineach burst.

In the “all bits spread over all bursts” method, as shown in FIG. 2,channel coding is performed on the control information of the primarybroadcast channel to which an error detecting code (cyclic redundancycheck: CRC) is attached. Then, an interleaving process is performed tointerleave (or reorder) bits constituting the channel-coded primarybroadcast channel, and the interleaved bits are mapped across multiplebursts. When a primary broadcast channel the bits of which are mappedacross multiple bursts is transmitted, the mobile station performs blinddetection where the primary broadcast channel received at each of allpossible timings is decoded and the correct timing is selected based onCRC check results. For example, as shown in FIG. 3, the mobile stationreceives the primary broadcast channel at each of timings 1 through 4and checks its CRC. Based on CRC check results, the mobile stationselects the correct timing, timing 1 in this example.

With this method, however, the mobile station has to try all fourcandidate reception timings and therefore it takes time to detect thecorrect timing. Also, with this method, at a timing (timing 2 in FIG. 3)that is 10 ms away from the correct timing, the CRC check result maybecome “good” because three of the four bursts received are correct.This may results in low detection accuracy.

In the “all bits in each burst” method, as shown in FIG. 4, channelcoding is performed on the control information of the primary broadcastchannel to which an error detecting code (cyclic redundancy check: CRC)is attached. The channel-coded primary broadcast channel is repeated (orduplicated) to generate, for example, four channel-coded primarybroadcast channels (bursts), and an interleaving process is performed tointerleave (or reorder) bits constituting each of the channel-codedprimary broadcast channels. Then, the interleaved bits are mapped. Whena primary broadcast channel all of the bits of which are mapped in eachburst is transmitted, the mobile station can obtain information by justreceiving one primary broadcast channel. Thus, this method makes itpossible to reduce the delay in reception processing. With this method,however, the mobile station cannot detect the primary broadcast channeltransmission cycle.

One object of the present invention is to solve or reduce one or more ofthe above problems and to provide a base station and a broadcast channeltransmission method that enable a user device to detect a transmissioncycle of a broadcast channel while reducing the time necessary toreceive the broadcast channel.

Means for Solving the Problems

An aspect of the present invention provides a base station thattransmits a broadcast channel to a user device a predefined number oftimes in a predetermined cycle for communication with the user device.The base station includes a repetition unit configured to repeat thebroadcast channel, after the broadcast channel is channel-coded, for thepredefined number of times to generate multiple broadcast channels; anda signal waveform changing unit configured to process the generatedbroadcast channels such that the processed broadcast channels havedifferent signal waveforms. Positions of the broadcast channels in theorder of transmission in the predetermined cycle are associated with thesignal waveforms of the broadcast channels.

Another aspect of the present invention provides a method oftransmitting a broadcast channel by a base station to a user device forcommunication with the user device where the broadcast channel istransmitted a predefined number of times in a predetermined cycle. Themethod includes a repetition step of repeating the broadcast channel,after the broadcast channel is channel-coded, for the predefined numberof times to generate multiple broadcast channels; and a signal waveformchanging step of processing the generated broadcast channels such thatthe processed broadcast channels have different signal waveforms thatare associated with positions of the broadcast channels in the order oftransmission in the predetermined cycle.

Advantageous Effect of the Invention

Aspects of the present invention provide a base station and a broadcastchannel transmission method that enable a user device to detect atransmission cycle of a broadcast channel while reducing the timenecessary to receive the broadcast channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating an exemplary method of transmitting aprimary broadcast channel;

FIG. 2 is a drawing illustrating an exemplary method of mapping aprimary broadcast channel;

FIG. 3 is a drawing illustrating an exemplary method of receiving aprimary broadcast channel;

FIG. 4 is a drawing illustrating an exemplary method of mapping aprimary broadcast channel;

FIG. 5 is a drawing illustrating a configuration of a radiocommunication system according to an embodiment of the presentinvention;

FIG. 6 is a drawing illustrating a radio frame structure;

FIG. 7 is a drawing illustrating TTI structures;

FIG. 8 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 9 is a drawing illustrating a subframe structure;

FIG. 10 is a drawing illustrating an example of subcarrier mapping atOFDM symbols #1 and #2;

FIG. 11 is a drawing illustrating an exemplary method of transmitting aprimary broadcast channel according to an embodiment of the presentinvention;

FIG. 12 is a flowchart showing a process of transmitting a primarycontrol channel according to an embodiment of the present invention;

FIG. 13 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 14 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 15 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 16 is a drawing illustrating a method of mapping a primarybroadcast channel according to an embodiment of the present invention;

FIG. 17 is a drawing illustrating a method of mapping a primarybroadcast channel according to an embodiment of the present invention;

FIG. 18 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention;

FIG. 19 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention;

FIG. 20 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention;

FIG. 21 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 22 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention;

FIG. 23 is a flowchart showing a scheduling process at a base stationaccording to an embodiment of the present invention;

FIG. 24 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention; and

FIG. 25 is a drawing illustrating exemplary subframe mapping accordingto an embodiment of the present invention.

EXPLANATION OF REFERENCES

-   -   50 _(k) (50 ₁, 50 ₂, 50 ₃) Cell    -   100 _(n) (100₁, 100 ₂, 100 ₃, 100 ₄, 100 ₅) User device    -   200 m (200₁, 200 ₂, 200 ₃) Base station    -   202 BCH control information generating unit    -   204 Channel coding unit    -   206 Repetition unit    -   208 Interleaving unit    -   210 Data modulation unit    -   212 Scrambling unit    -   214 Multiplexing-and-mapping unit    -   216 OFDM modulation unit    -   218 RF transmission unit    -   220 P-BCH transmission method control unit    -   222 Repetition-and-puncturing unit    -   224 Scheduler    -   300 Access gateway    -   400 Core network    -   1000 Radio communication system

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below with referenceto the accompanying drawings. Throughout the accompanying drawings, thesame reference numbers are used for parts having the same functions, andoverlapping descriptions of those parts are omitted.

A radio communication system 1000 including mobile stations and basestations according to an embodiment of the present invention isdescribed below with reference to FIG. 5.

The radio communication system 1000 is based on, for example, EvolvedUTRA and UTRAN (also called Long Term Evolution or Super 3G). The radiocommunication system 1000 includes base stations (eNode B: eNB) 200 _(m)(200₁, 200 ₂, 200 ₃, 200 _(m); m is an integer greater than 0) andmobile stations 100 _(n) (100₁, 100 ₂, 100 ₃, . . . , 100 _(n); n is aninteger greater than 0) that communicate with the base stations 200_(m). The base stations 200 _(m) are connected to an upper node such asan access gateway 300 and the access gateway 300 is connected to a corenetwork 400. Each of the mobile stations 100 _(n) is in one of cells 50_(k) (50 ₁, 50 ₂, 50 _(k); k is an integer greater than 0) andcommunicates with the corresponding one of the base stations 200 _(m)according to Evolved UTRA and UTRAN.

Some of the mobile stations 100 _(n) have already establishedcommunication channels with the base stations 200 _(m) and are incommunications; and the other mobile stations 100 _(n) have notestablished communication channels with the base stations 200 _(m) andare not in communications.

Each of the base stations 200 _(m) transmits synchronization signals.Each of the mobile stations 100 _(n) is located in one of the cells 50_(k) (50 ₁, 50 ₂, . . . , 50 _(k); k is an integer greater than 0). Whenthe mobile station 100 _(n) is, for example, turned on or in theintermittent reception mode during communications, the mobile station100 _(n) performs a cell search based on the synchronization signals tofind a cell that provides good radio communication quality for themobile station 100 _(n). More specifically, the mobile station 100 _(n)detects a symbol timing and a frame timing and detects cell-specificcontrol information such as a cell ID (a scrambling code unique to acell generated from the cell ID) or a group of cell IDs (hereaftercalled a cell ID group) based on the synchronization signals.

A cell search may be performed when the mobile station 100 _(n) is incommunications as well as when the mobile station 100 _(n) is not incommunications. For example, the mobile station 100 _(n) performs a cellsearch during communications to find a cell using the same frequency orto find a cell using a different frequency. The mobile station 100 _(n)also performs a cell search when it is not in communications, forexample, when the mobile station 100 _(n) has just been turned on or isin the standby mode.

The base stations 200 _(m) (200 ₁, 200 ₂, 200 ₃, . . . , 200 _(m)) havethe same configuration and functions and are therefore called the basestation 200, the base station 200 _(m), or the base stations 200 _(m) inthe descriptions below unless otherwise mentioned. The mobile stations100 _(n) (100 ₁, 100 ₂, 100 ₃, . . . , 100 _(n)) have the sameconfiguration and functions and are therefore called the mobile station100 _(n) or the mobile stations 100 _(n) (or user device 100) in thedescriptions below unless otherwise mentioned. The cells 50 _(k) (50 ₁,50 ₂, 50 ₃, . . . , 50 _(k)) have the same configuration and functionsand are therefore called the cell 50 _(k) or the cells 50 _(k) in thedescriptions below unless otherwise mentioned.

In the radio communication system 1000, orthogonal frequency divisionmultiplexing (OFDM) is used as the downlink radio access method andsingle-carrier frequency division multiple access (SC-FDMA) is used asthe uplink radio access method. In OFDM, as described above, a frequencyband is divided into narrow frequency bands (subcarriers) and data aretransmitted on the subcarriers. In SC-FDMA, a frequency band is dividedinto multiple frequency bands and the frequency bands are allocated todifferent terminals for transmission in order to reduce interferencebetween the terminals.

Communication channels used in Evolved UTRA and UTRAN are describedbelow.

For downlink, a physical downlink shared channel (PDSCH) shared by themobile stations 100 _(n) and an LTE downlink control channel are used.In downlink, the LTE downlink control channel is used to reportinformation on mobile stations to be mapped to the physical downlinkshared channel, transport format information for the physical downlinkshared channel, information on mobile stations to be mapped to aphysical uplink shared channel, transport format information for thephysical uplink shared channel, and acknowledgement information for thephysical uplink shared channel; and the physical downlink shared channelis used to transmit user data.

Also in downlink, the base stations 200 _(m) transmit synchronizationsignals used by the mobile stations 100 _(n) to perform cell searches.

For uplink, a physical uplink shared channel (PUSCH) shared by themobile stations 100 _(n) and an LTE uplink control channel are used.There are two types of uplink control channel: an uplink control channelto be time-division-multiplexed with the physical uplink shared channeland an uplink control channel to be frequency-division-multiplexed withthe physical uplink shared channel.

In uplink, the LTE uplink control channel is used to report downlinkchannel quality indicators (CQI) used for scheduling and adaptivemodulation and coding (AMC) of the physical downlink shared channel andto report acknowledgement information (HARQ ACK information) for thephysical downlink shared channel; and the physical uplink shared channelis used to transmit user data.

In downlink transmission, as shown in FIG. 6, one radio frame is 10 msand includes 10 TTIs. TTIs may also be called subframes. Also, as shownin FIG. 7, one TTI includes two subframes, and one subframe includesseven OFDM symbols when a short CP is used (upper half of FIG. 7) or sixOFDM symbols when a long CP is used (lower half of FIG. 7). When TTIsare called subframes, the subframes shown in FIG. 7 are called slots.

The base station 200 according to a first embodiment of the presentinvention is described below with reference to FIG. 8.

The base station 200 of this embodiment includes a BCH controlinformation generating unit 202, a channel coding unit 204, a repetitionunit 206, an interleaving unit 208, a data modulation unit 210, ascrambling unit 212 used as a spreading unit, a multiplexing-and-mappingunit 214, an OFDM modulation unit 216, an RF transmission unit 218, anda P-BCH transmission method control unit 220.

In this embodiment, it is assumed that the primary broadcast channel istransmitted multiple times in a primary broadcast channel transmissioncycle, and the base station 200 transmits respective bursts of theprimary broadcast channel using different methods. For example, the basestation 200 transmits bursts of the primary broadcast channel withdifferent signal waveforms. In this case, the signal waveforms of thebursts of the primary broadcast channel are associated with positions ofthe bursts in the order of transmission. For example, the respectivebursts of the primary broadcast channel are multiplied by differentscrambling codes such that the respective bursts have different signalwaveforms. In this embodiment, it is assumed that the primary broadcastchannel is transmitted four times in the primary broadcast channeltransmission cycle. Alternatively, the number of times the primarybroadcast channel is transmitted may be two, three, five, or more.

The BCH control information generating unit 202 generates controlinformation to be transmitted via broadcast channels. The size of thecontrol information is, for example, 40 bits. The broadcast channelsinclude a primary broadcast channel including minimum basic information(primary broadcast channel information) such as system frame numbers(SFN) and a public land mobile network ID (PLMNID); and a dynamicbroadcast channel used to transmit information other than the primarybroadcast channel information. Descriptions here are mainly related tothe primary broadcast channel. The BCH control information generatingunit 202 generates control information to be transmitted via the primarybroadcast channel for each primary broadcast channel transmission cycle.

The channel coding unit 204 performs channel coding on the controlinformation, i.e., the primary broadcast channel, generated by the BCHcontrol information generating unit 202. For example, the channel codingunit 204 includes a turbo encoder that performs error-correctionencoding to attach redundancy bits to information bits of the primarybroadcast channel.

The repetition unit 206 repeats (or duplicates) the channel-codedprimary broadcast channel for the number of times the primary broadcastchannel is to be transmitted in the primary broadcast channeltransmission cycle, thereby generates multiple, e.g., four, primarybroadcast channels (bursts), and inputs the primary broadcast channelsto the interleaving unit 208.

The interleaving unit 208 performs an interleaving process to interleave(or reorder) bits constituting each of the primary broadcast channelsaccording to a predetermined rule, and inputs the interleaved primarybroadcast channels to the data modulation unit 210.

The data modulation unit 210 data-modulates the channel-coded andinterleaved primary broadcast channels according to a predeterminedmodulation scheme, and inputs the data-modulated primary broadcastchannels to the scrambling (spreading) unit 212.

Meanwhile, the P-BCH transmission method control unit 220 assignsdifferent scrambling codes to the respective bursts of the primarybroadcast channel to be transmitted in a primary broadcast channeltransmission cycle. For example, assuming that the primary broadcastchannel is to be transmitted four times in a primary broadcast channeltransmission cycle, the P-BCH transmission method control unit 220prepares four different scrambling codes. In this case, the scramblingcodes are associated in advance with positions of the primary broadcastchannels (bursts) in the order of transmission.

The scrambling unit 212 spreads the primary broadcast channels inputfrom the data modulation unit 210 by the corresponding scrambling codesinput from the P-BCH transmission method control unit 220, and inputsthe spread primary broadcast channels to the multiplexing-and-mappingunit 214.

The multiplexing-and-mapping unit 214 receives the spread primarybroadcast channels from the scrambling unit 212 and also receives, forexample, a data channel and a reference signal. Themultiplexing-and-mapping unit 214 multiplexes the primary broadcastchannels, the data channel, and the reference signal.

FIG. 9 is a drawing illustrating exemplary mapping of the data channeland control channels. The primary broadcast channel is mapped in thesame center frequency band as that where the synchronization channel ismapped. The details of mapping are described later. In downlinktransmission, as shown in FIG. 9, one subframe is, for example, 1 ms andincludes 14 OFDM symbols. In FIG. 9, numbers (#1, #2, #3, . . . , #14)arranged along the time axis identify OFDM symbols, and numbers (#1, #2,#3, . . . , #M-1, #M; M is an integer greater than 0) arranged along thefrequency axis identify resource blocks.

The physical downlink control channel described above is mapped to first“N” OFDM symbols in a subframe. “N” may take a value of 1, 2, or 3. Inthe example of FIG. 9, the physical downlink control channel is mappedto the first two OFDM symbols (N=2), i.e., OFDM symbols #1 and #2, in asubframe. OFDM symbols other than those to which the physical downlinkcontrol channel is to be mapped are used to transmit user data, asynchronization channel (SCH), a broadcast channel (BCH), and a datasignal to which persistent scheduling is applied. The L1/L2 controlchannel and the data channel are time-division-multiplexed.

In the frequency direction, M resource blocks are defined. The bandwidthof each resource block is, for example, 180 kHz, and each resource blockincludes 12 subcarriers. The number of resource blocks M is 25 when thesystem bandwidth is 5 MHz, 50 when the system bandwidth is 10 MHz, or100 when the system bandwidth is 20 MHz.

FIG. 10 is a drawing illustrating an example of subcarrier mapping atOFDM symbols #1 and #2 in a subframe structure as shown in FIG. 9. InFIG. 10, the number of subcarriers for each OFDM symbol is L (L is aninteger greater than 0), and reference numbers #1, #2, . . . , #L areassigned to the subcarriers in ascending order of frequency. The numberof subcarriers L is 300 when the system bandwidth is 5 MHz, 600 when thesystem bandwidth is 10 MHz, or 1200 when the system bandwidth is 20 MHz.As shown in FIG. 10, a downlink reference signal (DL RS) and thephysical downlink control channel are mapped to subcarriers of OFDMsymbol #1. The physical downlink control channel is also mapped to OFDMsymbol #2. In this example, the L1/L2 control channel and other controlchannels are frequency-division-multiplexed such that each of thechannels is mapped to multiple frequency components arranged at certainintervals. Such a multiplexing scheme is called distributed frequencydivision multiplexing (FDM). Distributed FDM is preferable to achievefrequency diversity gain. The frequency components allocated to therespective channels may be arranged at the same intervals or atdifferent intervals. In either case, it is necessary to distribute theL1/L2 control channel across all resource blocks (in this embodiment,the entire system frequency band). CDM may also be used as an additionalmultiplexing scheme to cope with the increase in the number ofmultiplexed users. CDM makes it possible to further increase thefrequency diversity gain. On the other hand, however, CDM may disruptthe orthogonality and reduce the reception quality.

For example, in OFDM symbol #1, one DL RS is transmitted per sixsubcarriers. In FIG. 10, the DL RS is mapped to subcarriers withreference numbers “6×d−1” (d indicates 1, 2, . . . ). The physicaldownlink control channel is mapped to subcarriers other than those towhich the DL RS is mapped. In the example shown in FIG. 10,acknowledgement information (UL ACK/NACK) to be transmitted via thephysical downlink control channel is mapped to subcarrier #3 andsubcarrier #L-3. The number of subcarriers to which the acknowledgementinformation is mapped is determined by the maximum number of userdevices multiplexed in one subframe in uplink, i.e., the maximum numberof user devices that transmit uplink shared channels in one subframe.

In a case where the physical downlink control channel is mapped to threeOFDM symbols, the configuration of OFDM symbol #3 is substantially thesame as that of OFDM symbol #2.

The OFDM modulation unit 216 OFDM-modulates a signal where the datachannel, the reference signal, and the L1/L2 control channel aremultiplexed.

The RF transmission unit 218 attaches CPs to the signal where the datachannel, the reference signal, and the L1/L2 control channel aremultiplexed, performs digital-analog conversion, frequency conversion,and band limitation on the signal, amplifies the signal to anappropriate power level, and then transmits the signal.

As a result, as shown in FIG. 11, multiple, e.g., four, primarybroadcast channels spread by different scrambling codes are transmitted(i.e., the primary broadcast channel is transmitted four times) in aprimary broadcast channel transmission cycle. Thus, it is possible tovary signal waveforms of primary broadcast channels to be transmitted ina primary broadcast channel transmission cycle by spreading the primarybroadcast channels with different scrambling codes.

The user device 100 demodulates the primary broadcast channel by blinddetection where all predefined scrambling codes are tried to decode theprimary broadcast channel. Since multiple primary broadcast channels(bursts) are transmitted in a primary broadcast channel transmissioncycle by the “all bits in each burst” method, the user device 100 canobtain primary broadcast channel information by receiving just oneprimary broadcast channel, i.e., without receiving other primarybroadcast channels. This method makes it possible to reduce the timenecessary to receive the primary broadcast channel. Also, this methodmakes it possible to detect the position of a primary broadcast channelin the order of transmission by receiving only that one primarybroadcast channel and thereby to detect the boundary between primarybroadcast channel transmission cycles.

In related-art technologies, system frame numbers are assigned torespective frames. In the example shown in FIG. 11, system frame numbers#1-#8 are assigned to frames and therefore it is necessary to transmitthree information bits to report a system frame number. According tothis embodiment, since frames #1-#4 can be identified by a method basedon blind detection, it is necessary to transmit only one informationbit. Thus, this embodiment makes it possible to reduce the number ofinformation bits necessary to report system frame numbers.

The user device 100 has to receive broadcast channels even in thestandby mode. This embodiment allows the user device 100 to obtainprimary broadcast channel information by just receiving one primarybroadcast channel, i.e., without receiving other primary broadcastchannels. In other words, this embodiment eliminates the need for theuser device 100 to perform reception processing throughout the primarybroadcast channel transmission cycle. This in turn makes it possible tosave battery energy. Meanwhile, using different transmission methods forrespective bursts of the primary broadcast channel in a primarybroadcast channel transmission cycle makes it possible to achievediversity gain if the bursts are to be combined after reception.

Since the primary broadcast channel is transmitted multiple times in aprimary broadcast channel transmission cycle, the transmission powerlevel of each burst of the primary broadcast channel becomes low. Forthis reason, a user device at a cell edge may obtain primary broadcastchannel information by soft-combining multiple bursts of the primarybroadcast channel transmitted in a primary broadcast channeltransmission cycle. On the other hand, a user device near the center ofthe cell can obtain primary broadcast channel information withoutsoft-combining multiple bursts of the primary broadcast channeltransmitted in a primary broadcast channel transmission cycle.

The user device 100 may be configured to try adjacent scrambling codesin blind detection where all predefined scrambling codes are tried todecode the primary broadcast channel.

Next, a broadcast channel transmission method of this embodiment isdescribed with reference to FIG. 12.

The BCH control information generating unit 202 generates controlinformation to be transmitted via a primary broadcast channel (stepS1202).

The channel coding unit 204 performs channel coding on the controlinformation, i.e., the primary broadcast channel, generated by the BCHcontrol information generating unit 202 (step S1204).

The repetition unit 206 repeats (or duplicates) the channel-codedprimary broadcast channel for the number of times the primary broadcastchannel is transmitted in a primary broadcast channel transmission cycleto generate multiple primary broadcast channels (step S1206).

Then, the primary broadcast channels to be transmitted in the primarybroadcast channel transmission cycle are processed to have differentwaveforms (step S1208). For example, a process as described above isperformed by the P-BCH transmission method control unit 220.

Next, the base station 200 according to a second embodiment of thepresent invention is described with reference to FIG. 13.

The base station 200 of this embodiment has a configuration similar tothat described with reference to FIG. 8 except that arepetition-and-puncturing unit 222 is provided instead of the repetitionunit 206 and the P-BCH transmission method control unit 220 is connectedto the repetition-and-puncturing unit 222.

The P-BCH transmission method control unit 220 assigns differentpuncturing patterns, which are used to puncture redundancy bits attachedto the information bits of the primary broadcast channel, to therespective bursts of the primary broadcast channel to be transmitted inthe primary broadcast channel transmission cycle. For example, assumingthat the primary broadcast channel is to be transmitted four times in aprimary broadcast channel transmission cycle, the P-BCH transmissionmethod control unit 220 prepares four different puncturing patterns. Inthis case, the puncturing patterns are associated in advance withpositions of primary broadcast channels (bursts) in the order oftransmission.

The repetition-and-puncturing unit 222 repeats (or duplicates) theprimary broadcast channel for the number of times the primary broadcastchannel is to be transmitted in a primary broadcast channel transmissioncycle to generate multiple, e.g., four, primary broadcast channels(bursts), and punctures redundancy bits attached to the information bitsof the respective primary broadcast channels based on the puncturingpatterns input from the P-BCH transmission method control unit 220.

As a result, multiple, e.g., four, primary broadcast channels puncturedby different puncturing patterns are transmitted (i.e., the primarybroadcast channel is transmitted four times) in a primary broadcastchannel transmission cycle. Thus, it is possible to vary signalwaveforms of primary broadcast channels to be transmitted in a primarybroadcast channel transmission cycle by puncturing the primary broadcastchannels with different puncturing patterns.

The user device 100 demodulates the primary broadcast channel by blinddetection where all predefined puncturing patterns are tried to decodethe primary broadcast channel. Since multiple primary broadcast channels(bursts) are transmitted in a primary broadcast channel transmissioncycle by the “all bits in each burst” method, the user device 100 canobtain primary broadcast channel information by receiving just oneprimary broadcast channel, i.e., without receiving other primarybroadcast channels. This method makes it possible to reduce the timenecessary to receive the primary broadcast channel. Also, this methodmakes it possible to detect the position of a primary broadcast channelin the order of transmission by receiving only that one primarybroadcast channel and thereby to detect the boundary between primarybroadcast channel transmission cycles.

Further, varying signal waveforms by using different puncturing patternsmakes it possible to achieve channel coding gain.

Next, the base station 200 according to a third embodiment of thepresent invention is described with reference to FIG. 14.

The base station 200 of this embodiment has a configuration similar tothat described with reference to FIG. 8 except that the P-BCHtransmission control unit 220 is connected to the interleaving unit 208.

The P-BCH transmission method control unit 220 assigns differentinterleaving patterns, which are used by the interleaving unit 208 tointerleave (or reorder) the information bits and the redundancy bits, tothe respective bursts of the primary broadcast channel. Here, theinterleaving patterns indicate patterns or rules for interleaving thebits. For example, assuming that the primary broadcast channel is to betransmitted four times in a primary broadcast channel transmissioncycle, the P-BCH transmission method control unit 220 prepares fourdifferent interleaving patterns.

In this case, the interleaving patterns are associated in advance withpositions of the primary broadcast channels (bursts) in the order oftransmission.

The interleaving unit 208 performs an interleaving process to interleave(or reorder) bits constituting the respective primary broadcast channelsbased on the interleaving patterns input from the P-BCH transmissionmethod control unit 220, and inputs the processed primary broadcastchannels to the data modulation unit 210.

As a result, multiple, e.g., four, primary broadcast channels on whichthe interleaving process is performed based on different interleavingpatterns are transmitted (i.e., the primary broadcast channel istransmitted four times) in a primary broadcast channel transmissioncycle. Thus, it is possible to vary signal waveforms of primarybroadcast channels to be transmitted in a primary broadcast channeltransmission cycle by interleaving bits of the respective primarybroadcast channels with different interleaving patterns.

The user device 100 demodulates the primary broadcast channel by blinddetection where all predefined interleaving patterns are tried to decodethe primary broadcast channel. Since multiple primary broadcast channels(bursts) are transmitted in a primary broadcast channel transmissioncycle by the “all bits in each burst” method, the user device 100 canobtain primary broadcast channel information by receiving just oneprimary broadcast channel, i.e., without receiving other primarybroadcast channels. This method makes it possible to reduce the timenecessary to receive the primary broadcast channel. Also, this methodmakes it possible to detect the position of a primary broadcast channelin the order of transmission by receiving only that one primarybroadcast channel and thereby to detect the boundary between primarybroadcast channel transmission cycles.

Further, varying signal waveforms by using different interleavingpatterns makes it possible to achieve frequency diversity gain.

Next, the base station 200 according to a fourth embodiment of thepresent invention is described with reference to FIG. 15.

The base station 200 of this embodiment has a configuration similar tothat described with reference to FIG. 8 except that the P-BCHtransmission control unit 220 is connected to themultiplexing-and-mapping unit 214.

The P-BCH transmission method control unit 220 controls themultiplexing-and-mapping unit 214 to map respective bursts of theprimary broadcast channel to different radio resources. For example,assuming that the primary broadcast channel is to be transmitted fourtimes in a primary broadcast channel transmission cycle, the P-BCHtransmission method control unit 220 prepares four different radioresources. In this case, the radio resources are associated in advancewith positions of the primary broadcast channels (bursts) in the orderof transmission.

The multiplexing-and-mapping unit 214 multiplexes the spread primarybroadcast channels input from the scrambling unit 212, the data channel,and the reference signal based on radio resource information input fromthe P-BCH transmission method control unit 220.

As a result, multiple, e.g., four, primary broadcast channels aretransmitted (i.e., the primary broadcast channel is transmitted fourtimes) using different radio resources in a primary broadcast channeltransmission cycle.

Thus, it is possible to vary signal waveforms of primary broadcastchannels to be transmitted in a primary broadcast channel transmissioncycle by allocating different radio resources to the primary broadcastchannels.

The user device 100 demodulates the primary broadcast channel by blinddetection where all predefined radio resources are tried to decode theprimary broadcast channel. Since multiple primary broadcast channels(bursts) are transmitted in a primary broadcast channel transmissioncycle by the “all bits in each burst” method, the user device 100 canobtain primary broadcast channel information by receiving just oneprimary broadcast channel, i.e., without receiving other primarybroadcast channels. This method makes it possible to reduce the timenecessary to receive the primary broadcast channel. Also, this methodmakes it possible to detect the position of a primary broadcast channelin the order of transmission by receiving only that one primarybroadcast channel and thereby to detect the boundary between primarybroadcast channel transmission cycles.

Further, for example, allocating different frequency bands or resourceblocks to the respective bursts of the primary broadcast channel makesit possible to achieve frequency diversity gain.

Next, the base station 200 according to a fifth embodiment of thepresent invention is described.

In 3GPP Evolved UTRA and UTRAN, a system bandwidth is between 1.25 MHzand 20 MHz. In this embodiment, the base station 200 transmits thebroadcast channel using, for example, a 1.08 MHz frequency bandincluding the center frequency. Also, the broadcast channel ispreferably transmitted in the same center frequency band as that usedfor transmission of the synchronization channel. This configurationenables the mobile station to receive the broadcast channel withoutchanging the center frequency after a cell search and thereby to reducetime necessary to receive minimum system information. The centerfrequency of the broadcast channel is preferably the center of thesystem bandwidth. This makes it possible to simplify the receptionprocessing at the mobile station.

The base station 200 of this embodiment has a configuration as describedabove and employs precoding vector switching (PVS) to achievetransmission diversity. In PVS, each primary broadcast channel in aprimary broadcast channel transmission cycle is multiplied by differentweights for transmission from multiple antennas, e.g., antenna #1 andantenna #2. In this case, the synchronization channel and the primarybroadcast channel are transmitted using the same precoding vector. Thismethod enables the user device 100 to perform channel estimation usingthe synchronization channel as a reference. The user device 100demodulates the primary broadcast channel on an assumption that theprimary broadcast channel is transmitted using the same precoding vectoras that used for the synchronization channel. Therefore, it is notnecessary to report to the user device 100 whether transmissiondiversity is employed. For example, it is not necessary to report atransmission diversity mode such as the number of antennas via thesecondary synchronization channel. This also applies to a case whereonly one antenna is used for transmission.

Thus, this method enables the user device 100 to use soft combining toreceive the primary broadcast channel and thereby to achieve diversitygain. Soft combining is applied to adjacent cells.

As shown in FIG. 16, the multiplexing-and-mapping unit 214 maps theprimary broadcast channel across the same center frequency band as thatwhere the synchronization channel is mapped. Themultiplexing-and-mapping unit 214 may be configured to map respectiveprimary broadcast channels to be transmitted in a primary broadcastchannel transmission cycle to different OFDM symbols. Also, to improvethe accuracy of channel estimation based on the synchronization channel,it is preferable to map the primary broadcast channel to OFDM symbolsadjacent to those to which the synchronization channel is mapped.

Mapping the primary broadcast channel across the same center frequencyband as that where the synchronization channel is mapped makes itpossible to achieve frequency diversity gain. Also, mapping the primarybroadcast channel to a part of OFDM symbols in a subframe enables theuser device 100 to receive the primary broadcast channel within a shortperiod of time. This in turn makes it possible to save battery energy.Being able to complete reception of the primary broadcast channel withina short period of time is particularly preferable when the user device100 is in the intermittent reception (DRX) mode. Also, since only a partof OFDM symbols are used, it is easy to switch the short CP to the longCP and vice versa.

Next, the base station 200 according to a sixth embodiment of thepresent invention is described.

In 3GPP Evolved UTRA and UTRAN, a system bandwidth is between 1.25 MHzand 20 MHz. In this embodiment, the base station 200 transmits thebroadcast channel using, for example, a part of a 1.08 MHz frequencyband including the center frequency. Also, the broadcast channel ispreferably transmitted in the same center frequency band as that usedfor transmission of the synchronization channel. This configurationenables the mobile station to receive the broadcast channel withoutchanging the center frequency after a cell search and thereby to reducetime necessary to receive minimum system information. The centerfrequency of the broadcast channel is preferably the center of thesystem bandwidth. This makes it possible to simplify the receptionprocessing at the mobile station.

The base station 200 of this embodiment has a configuration as describedabove and employs space frequency block coding (SFBC) to achievetransmission diversity. In this case, a reference signal is used forchannel estimation when receiving the primary broadcast channel.

As shown in FIG. 17, the multiplexing-and-mapping unit 214 maps theprimary broadcast channel in the same center frequency band as thatwhere the synchronization channel is mapped. The primary broadcastchannel and the shared data channel are frequency-division-multiplexedsuch that each of the channels is mapped to multiple frequencycomponents arranged at certain intervals. Such a multiplexing scheme iscalled distributed frequency division multiplexing (FDM). DistributedFDM is preferable to achieve frequency diversity gain. In the exampleshown in FIG. 17, a frequency band that is an integral multiple of aresource block is allocated to the primary broadcast channel. In otherwords, the primary broadcast channel and the shared data channel aremultiplexed based on resource blocks. This method makes it possible toreduce the transmission power to be allocated to the shared data channeland to allocate extra transmission power obtained by the reduction tothe primary broadcast channel. That is, this method enables powerboosting.

Next, the base station 200 according to a seventh embodiment of thepresent invention is described.

As described with reference to FIG. 16, the base station 200 of thisembodiment maps the primary broadcast channel across the same centerfrequency band as that where the synchronization channel is mapped, forexample, across a 1.08 MHz frequency band including the centerfrequency. For example, the primary broadcast channel is mapped to OFDMsymbols adjacent to those used for the synchronization channel.

In the example shown in FIG. 18 where the data amount of the primarybroadcast channel is about four symbols, resource elements (REs)corresponding to symbols 10-14 in subframe #0 in the center frequencyband are left unused and available for other channels. Here, a resourceelement indicates a radio resource composed of one OFDM symbol and onesubcarrier. Thus, resource elements in the center frequency band otherthan those allocated to the physical downlink control channel, thereference signal, the synchronization channel, and the primary broadcastchannel are available for other channels.

Similarly, in the example shown in FIG. 19, resource elementscorresponding to symbols 4-5 and 8-14 in subframe #5 in the centerfrequency band are left unused and available for other channels. Inother words, resource elements in the center frequency band other thanthose allocated to the physical downlink control channel, the referencesignal, and the synchronization channel are available for otherchannels.

Also, in the example shown in FIG. 20, resource elements correspondingto symbols 4-14 in subframes other than subframes #0 and #5 in thecenter frequency band are left unused and available for other channels.In other words, resource elements in the center frequency band otherthan those allocated to the physical downlink control channel and thereference signal are available for other channels.

In subframes other than subframes #0 and #5 described above, the numberof resource elements other than those allocated to the physical downlinkcontrol channel and the reference signal in each resource block(hereafter called a resource block size) in the center frequency band isthe same as that number (or the resource block size) in other frequencybands in the system frequency band. Therefore, scheduling can beperformed without any problem.

Meanwhile, in subframes #0 and #5 described above, the number ofavailable symbols or resource elements in each resource block (or theresource block size) in the center frequency band is different from thatnumber (or the resource block size) in other frequency bands in thesystem frequency band. Therefore, it is necessary to perform schedulingtaking into account resource block sizes.

The center frequency band has a size of six resource blocks in thefrequency direction. The base station 200 of this embodiment maps abroadcast channel to be transmitted via the physical downlink sharedchannel, i.e., the dynamic broadcast channel, to the available(remaining) resource elements. Also, the base station 200 of thisembodiment may be configured to allocate some of the available resourceelements preferentially to the broadcast channel to be transmitted viathe physical downlink shared channel and to allocate still remainingresource elements to a data channel.

The base station 200 of this embodiment is described below withreference to FIG. 21.

The base station 200 of this embodiment has a configuration similar tothat described with reference to any one of FIGS. 8, 13, 14, and 15, andfurther includes a scheduler (control unit) 224 connected to themultiplexing-and-mapping unit 214.

As shown in FIG. 22, the scheduler 224 performs scheduling for thecenter frequency band based on (or in units of) resource blocks in amanner similar to the scheduling for other frequency bands in the systemfrequency band. In this embodiment, as described above, the size ofresource blocks or the number of available resource elements in eachresource block in the center frequency band is different from that inother frequency bands in the system frequency band. Therefore, thescheduler 224 allocates resource blocks in the center frequency band tothe broadcast channel to be transmitted via the physical downlink sharedchannel based on the size of the resource blocks. FIG. 22 shows anexample of mapping in subframe #0. However, scheduling for subframe #5is also performed in a similar manner based on resource blocks.

Here, scheduling indicates a process of selecting mobile stationsallowed to communicate using a shared channel for each subframe (1 ms).For example, scheduling is performed based on CQIs reported via uplinkby mobile stations. Also in the scheduling, resource blocks used foruser data to be received by the selected mobile stations are determined.

Thus, in this embodiment, scheduling for the center frequency band isalso performed based on resource blocks in a manner similar to thescheduling for other frequency bands in the system frequency band. Withthis method, since scheduling for the center frequency band andscheduling for other frequency bands are performed based on the samephysical layer units, i.e., resource blocks, it is possible to unifyformats of control signals for resource allocation.

Next, a process performed by the scheduler 224 of the base station 200of this embodiment is described with reference to FIG. 23.

The scheduler 224 sets a subframe number t at 0 (step S2302).

Next, the scheduler 224 calculates weights of 0 resource blocks (RBs)for respective users (step S2304). For example, weights are calculatedbased on CQIs reported for respective RBs via uplink by each mobilestation. Also, the traffic wait time, data sizes, and traffic types ofusers and radio resource sizes of RBs may also be taken into account incalculating weights of RBs for the users. The traffic wait time includesdelay time and the traffic type includes acceptable delay and anacceptable packet error rate. More particularly, in subframes #0 and #5,weights of RBs are calculated for respective users based on resourceblock sizes.

The scheduler 224 allocates radio resources of the RBs based on thecalculated weights (step S2306). Then, transmission processing isperformed (step S2308).

The scheduler 224 sets the subframe number t at t+1 (step 52310) andreturns to step 52304 to perform scheduling for the next subframe.

In this embodiment, scheduling is performed based on an assumption thatthere are resource blocks with different radio resource sizes. In otherwords, scheduling is performed based on resource block sizes.

Next, the base station 200 according to an eighth embodiment of thepresent invention is described.

As described with reference to FIG. 16, the base station 200 of thisembodiment maps the primary broadcast channel across the same centerfrequency band as that where the synchronization channel is mapped. Forexample, the primary broadcast channel is mapped to OFDM symbolsadjacent to those used for the synchronization channel.

In the example shown in FIG. 18 where the data amount of the primarybroadcast channel is about four symbols, resource elements correspondingto symbols 10-14 in subframe #0 in the center frequency band are leftunused and available for other channels. In other words, resourceelements in the center frequency band other than those allocated to thephysical downlink control channel, the reference signal, thesynchronization channel, and the primary broadcast channel are availablefor other channels.

Similarly, in the example shown in FIG. 19, resource elementscorresponding to symbols 4-5 and 8-14 in subframe #5 in the centerfrequency band are left unused and available for other channels. Inother words, resource elements in the center frequency band other thanthose allocated to the physical downlink control channel, the referencesignal, and the synchronization channel are available for otherchannels.

Also, in the example shown in FIG. 20, resource elements correspondingto symbols 4-14 in subframes other than subframes #0 and #5 in thecenter frequency band are left unused and available for other channels.In other words, resource elements in the center frequency band otherthan those allocated to the physical downlink control channel and thereference signal are available for other channels.

In subframes other than subframes #0 and #5 described above, the numberof resource elements other than those allocated to the physical downlinkcontrol channel and the reference signal in each resource block (or theresource block size) in the center frequency band is the same as thatnumber (or the resource block size) in other frequency bands in thesystem frequency band. Therefore, scheduling can be performed withoutany problem.

Meanwhile, in subframes #0 and #5 described above, the number ofresource elements other than those allocated to the physical downlinkcontrol channel and the reference signal in each resource block (or theresource block size) in the center frequency band is different from thatnumber (or the resource block size) in other frequency bands in thesystem frequency band. Therefore, it is necessary to perform schedulingtaking into account resource block sizes.

The center frequency band has a size of six resource blocks in thefrequency direction. The base station 200 of this embodiment maps abroadcast channel to be transmitted via the physical downlink sharedchannel, i.e., the dynamic broadcast channel, to the available(remaining) resource elements. Also, the base station 200 of thisembodiment may be configured to allocate some of the available resourceelements preferentially to the broadcast channel to be transmitted viathe physical downlink shared channel and to allocate still remainingresource elements to a data channel.

The configuration of the base station 200 of this embodiment issubstantially the same as that described with reference to FIG. 21.

As shown in FIG. 24, the scheduler 224 groups resource elements in thecenter frequency band other than those allocated to the physicaldownlink control channel, the reference signal, the synchronizationchannel, and the primary broadcast channel such that the number ofresource elements in each group becomes the same as the number ofresource elements in each resource block in other frequency bands in thesystem frequency band. For example, each resource block in the otherfrequency bands in the system frequency band is composed of 11 symbolsand 12 subcarriers (=180 kHz) and therefore includes 11×12=132 resourceelements. Meanwhile, in the center frequency band, only five symbols areavailable. Therefore, to form a resource block having the same size asthat in the other frequency bands, 132/5=26.5 subcarriers are necessary.In this example, the center frequency band is divided into two to formtwo resource blocks. In actual cases, the number of resource elements ineach resource block in the center frequency band becomes greater thanthe number of resource elements in each resource block in frequencybands other than the center frequency band. The surplus resourceelements may be used, for example, for repetition to increase dataredundancy, or may be reserved for future use as shown in FIG. 25. Usingthe surplus resource elements for repetition makes it possible toimprove communication quality.

The scheduler 224 performs scheduling based on (or in units of) resourceblocks. In this embodiment, as described above, the size of resourceblocks or the number of resource elements in each resource block in thecenter frequency band is substantially the same as that in otherfrequency bands in the system frequency band. This makes it possible touse substantially the same channel coding rate and to achievesubstantially the same communication quality for resource blocks in thecenter frequency band and other frequency bands.

Here, scheduling indicates a process of selecting mobile stationsallowed to communicate using a shared channel for each subframe (1 ms).For example, scheduling is performed based on CQIs reported via uplinkby mobile stations. In a case where each mobile station reports CQIs ofrespective resource blocks, a CQI of a resource block in the centerfrequency band is represented by an average of CQIs of frequency bandscorresponding to the resource block. Also in the scheduling, resourceblocks used for user data to be received by the selected mobile stationsare determined.

Thus, making the number of resource elements in each resource block inthe center frequency band the same as the number of resource elements ineach resource block in other frequency bands in the system frequencyband makes it possible to simplify the scheduling process at the basestation 200.

In the above embodiments, it is assumed that a system based on EvolvedUTRA and UTRAN (also called Long Term Evolution or Super 3G) is used.However, a base station and a broadcast channel transmission methodaccording to the present invention may also be applied to any systememploying orthogonal frequency division multiplexing (OFDM) fordownlink.

Although the present invention is described above in differentembodiments, the distinctions between the embodiments are not essentialfor the present invention, and the embodiments may be implementedindividually or in combination. Although specific values are used in theabove descriptions to facilitate the understanding of the presentinvention, the values are just examples and different values may also beused unless otherwise mentioned.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention. Although functionalblock diagrams are used to describe apparatuses in the aboveembodiments, the apparatuses may be implemented by hardware, software,or a combination of them.

The present international application claims priority from JapanesePatent Application No. 2007-161947 filed on Jun. 19, 2007 and JapanesePatent Application No. 2007-211599 filed on Aug. 14, 2007, the entirecontents of which are hereby incorporated herein by reference.

1. A base station transmitting a broadcast channel to a user device apredefined number of times in a predetermined cycle for communicationwith the user device, the base station comprising: a repetition unitconfigured to repeat the broadcast channel, after the broadcast channelis channel-coded, for the predefined number of times to generatemultiple broadcast channels; a signal waveform changing unit configuredto process the generated broadcast channels such that the processedbroadcast channels have different signal waveforms, wherein positions ofthe broadcast channels in order of transmission in the predeterminedcycle are associated with the signal waveforms of the broadcastchannels; an interleaving unit configured to interleave information bitsof the respective broadcast channels generated by the repetition unit; adata modulation unit configured to data-modulate the interleavedbroadcast channels; and a spreading unit configured to multiply thedata-modulated broadcast channels by scrambling codes, wherein thesignal waveform changing unit is configured to control the spreadingunit to multiply the respective data-modulated broadcast channels bydifferent scrambling codes.
 2. The base station as claimed in claim 1,wherein the signal waveform changing unit is configured to puncture thebroadcast channels generated by the repetition unit using differentpuncturing patterns.
 3. The base station as claimed in claim 1, furthercomprising: an interleaving unit configured to interleave informationbits of the respective broadcast channels generated by the repetitionunit, wherein the signal waveform changing unit is configured to controlthe interleaving unit to interleave the information bits of therespective broadcast channels based on different interleaving patterns.4. The base station as claimed in claim 1, further comprising: aninterleaving unit configured to interleave information bits of therespective broadcast channels generated by the repetition unit; a datamodulation unit configured to data-modulate the interleaved broadcastchannels; a spreading unit configured to multiply the data-modulatedbroadcast channels by scrambling codes; and a mapping unit configured tomap the multiplied broadcast channels in a center frequency band in asystem frequency band, wherein the signal waveform changing unit isconfigured to control the mapping unit to map the respective multipliedbroadcast channels to different radio resources.
 5. The base station asclaimed in claim 4, wherein the mapping unit is configured to map thebroadcast channels across the same center frequency band as that where asynchronization channel is mapped.
 6. The base station as claimed inclaim 5, further comprising: a scheduler configured to select, for eachsubframe, one or more mobile stations allowed to communicate using ashared channel and to determine resource blocks used for user data to bereceived by the selected mobile stations, wherein the mapping unit isconfigured to map a broadcast channel including information on thedetermined resource blocks and to be transmitted via a physical downlinkshared channel to one or more resource blocks in the same centerfrequency band as that where the synchronization channel is mapped. 7.The base station as claimed in claim 6, wherein a bandwidth of theresource blocks in the center frequency band is the same as a bandwidthof resource blocks in frequency bands other than the center frequencyband.
 8. The base station as claimed in claim 7, wherein a size of theresource blocks in the center frequency band is the same as a size ofthe resource blocks in the frequency bands other than the centerfrequency band.
 9. The base station as claimed in claim 4, wherein themapping unit is configured to map the broadcast channels in a part ofthe same center frequency band as that where a synchronization channelis mapped.
 10. A method of transmitting a broadcast channel by a basestation to a user device for communication with the user device wherethe broadcast channel is transmitted a predefined number of times in apredetermined cycle, the method comprising: a repetition step ofrepeating the broadcast channel, after the broadcast channel ischannel-coded, for the predefined number of times to generate multiplebroadcast channels; a signal waveform changing step of processing thegenerated broadcast channels such that the processed broadcast channelshave different signal waveforms that are associated with positions ofthe broadcast channels in order of transmission in the predeterminedcycle; an interleaving step of interleaving information bits of therespective broadcast channels generated by the repetition step; a datamodulation step of data-modulating the interleaved broadcast channels;and a spreading step of multiplying the data-modulated broadcastchannels by scrambling codes, wherein the signal waveform changing stepcontrols the spreading step to multiply the respective data-modulatedbroadcast channels by different scrambling codes.